When routing wide grooves and rabbets onto the sides, edges, or ends of boards, it is desirable to provide an apparatus which readily adjusts to the height of the workpiece and the width of the groove required.
Various designs can be found in the prior art including Spielman, P., The New Router Handbook (New York: Sterling Publishing Co., 1993) at pp. 137, 138, and 154-155. As described on p. 137, and shown in illus. 11-7 and 11-8, a pair of edge guides can be attached to the router base and can be used as fences which run along each side of a workpiece. The apparatus shown in illus. 11-7 and 11-8 does not allow the routing of wide grooves or recesses, and essentially enables routing of a groove of the same width as the router bit.
Another design is shown at p. 154, in illus. 12-1. As shown in illus. 12-1, a hand-held router is mounted onto a board having two adjustable side fences mounted into parallel slots on either side. The side fences butt up against two fixed and level router guide rails which contain a board to be planed by a router, as shown in illus. 12-3. While this design allows wide grooves or recesses to be routed into a workpiece, two fixed and level guide rails are required, and the adjustable guide fences on either side cannot be readily set to rout a groove having a particular width.
Another design is disclosed in Spielman, P., Router Jigs and Techniques (New York: Sterling Publishing Co., 1988) at pp. 203-205. In illus. 438-441, a hand-held router is shown with parallel runners attached to the base of the router. These runners act to suspend the hand-held router above a workpiece and cannot be adjusted laterally. Consequently, this design cannot be used to form grooves having various width. A variation of this design, shown in illus. 443-445, also cannot be used for this purpose, particularly because the U-shape of the one piece runner will not allow the router to be moved along the length of a workpiece, and these designs are essentially intended for planing operations of wood plugs or pegs.
Other designs are shown in De Cristoforo, R. J., The Portable Router Book, 2nd Edition (Blue Ridge Summit, PA: TAB Books, 1994) at pp. 131-136 and 214-218. As described on pp. 131-133, and as illustrated in FIGS. 9-20 and 9-22, a special router sub-base is shown having adjustable guide fences attached on either side. This design potentially allows a hand-held router to be used to rout wide grooves or slots. However, this special router sub-base must be supported on two level rails which clamp a workpiece between them. Consequently, the width of the groove or slot being cut will be limited by the rails on either side of the workpiece, as shown in FIGS. 9-21. Furthermore, as shown in FIGS. 9-23, on p. 134, the guides on the sub-base are designed to be set so that both guides are guided along the outside of the clamping rails. A somewhat different design, allowing grooves to be automatically centered in the workpiece, is shown in FIGS. 9-26, and demonstrated in FIGS. 9-27 and 9-28. By a pivoting action of the router base, the attached rails are twisted into a parallelogram shape which hugs the workpiece as shown. While this design is useful for centering a groove in a workpiece, it is not suitable for routing wide grooves or recesses of various width.
Finally, L-shaped tracks are disclosed in FIGS. 11-19 for levelling the top of a number of slabs which have been glued together. However, the L-shaped tracks are connected at each end by track connectors, which rest and slide along bearing strips located on each side of the workpiece. Consequently, the width of the L-shaped tracks are not adjustable.